Help with a Workflow trigger

Hi,

I am trying to create a workflow trigger that will prevent a record from saving when an owner is changed by someone outside their business channel.

The scenarios to trigger the workflow are: 1. the current owner and new owner are in different channels.  2. the user has not checked a 'consent' box and/or has not filled in the consent text box.

I have a similar workflow setup on the contact object which works fine, but on the account object it doesn't work -- it fires off every time i change the owner, ignoring the consent check box / text box validation.